Enigmatic relationship between chlorophyll a concentrations and photosynthetic rates at Station ALOHA.

An ordinary least squares (OLS) analysis of the relationship between chlorophyll a (chl a) concentrations and photosynthetic rates at depths of 5 and 25 m at Station ALOHA produced a slope that was only 28% of the mean productivity index at those depths and an intercept at zero chl a that equaled 70% of the mean photosynthetic rate. OLS regression lines are known to produce a slope and intercept that are biased estimates of the true slope and intercept when the explanatory variable, X, is uncontrolled, but in this case the measurement errors and natural variability of the chl a concentrations were much too small to explain the apparent bias. The bias was traceable to the fact that the photosynthetic rates were determined by more than one explanatory variable, a source of variability that is typically overlooked in discussions of OLS bias. Modeling the photosynthetic rates as a function of the product of chl a and surface irradiance produced a much more accurate and realistic description of the data, but the OLS continued to be biased, presumably because the photosynthetic rates were functions of factors in addition to chl a and surface irradiance (e.g., temperature, macronutrients, trace metals, and vitamins). The results underscore the need to recognize that the absence of bias in an OLS when X is not controlled implies that all scatter in the data about the OLS is due to errors in the dependent variable, an unlikely scenario. In most cases, resolution of the bias problem will require identification of the explanatory variables in addition to X that determine the dependent variable.

Prominent human health impacts from several marine microbes: history, ecology, and public health implications.

This paper overviews several examples of important public health impacts by marine microbes and directs readers to the extensive literature germane to these maladies. These examples include three types of dinoflagellates (Gambierdiscus spp., Karenia brevis, and Alexandrium fundyense), BMAA-producing cyanobacteria, and infectious microbes. The dinoflagellates are responsible for ciguatera fish poisoning, neurotoxic shellfish poisoning, and paralytic shellfish poisoning, respectively, that have plagued coastal populations over time. Research interest on the potential for marine cyanobacteria to contribute BMAA into human food supplies has been derived by BMAA's discovery in cycad seeds and subsequent implication as the putative cause of amyotrophic lateral sclerosis/parkinsonism dementia complex among the Chamorro people of Guam. Recent UPLC/MS analyses indicate that recent reports that BMAA is prolifically distributed among marine cyanobacteria at high concentrations may be due to analyte misidentification in the analytical protocols being applied for BMAA. Common infectious microbes (including enterovirus, norovirus, Salmonella, Campylobacter, Shigella, Staphylococcus aureus, Cryptosporidium, and Giardia) cause gastrointestinal and skin-related illness. These microbes can be introduced from external human and animal sources, or they can be indigenous to the marine environment.

Consistent fractionation of 13C in nature and in the laboratory: growth-rate effects in some haptophyte algae.

The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate. Specifically, if the fractionation is expressed by epsilon p approximately delta e - delta p, where delta e and delta p are the delta 13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, micromole kg-1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, microM, and b = (25 - epsilon p)Ce. The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth. The relationship reported here is characteristic of 39 samples (r2 = 0.95) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone. Points representative of samples from the Sargasso Sea ([PO4] < or = 0.1 microM) fall above the b = f[PO4] line. Analysis of correlations expected between mu (growth rate), epsilon p, and Ce shows that, for our entire data set, most variations in epsilon p result from variations in mu rather than Ce. Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera.

A study of the energetics and economics of microalgal mass culture with the marine chlorophyte Tetraselmis suecica: Implications for use of power plant stack gases.

The marine phytoplankter Tetraselmis suecica was grown in shallow outdoor flumes for a period of approximately 6 months at the Natural Energy Laboratory of Hawaii. In full sunlight, gross production rates were 15-20 g C m(-2) d(-1). The corresponding photosynthetic efficiencies (PE's) were 9-10%. Respiration losses removed about half the gross production. The CO(2) utilization efficiencies of 96 +/- 11% were achieved by bubbling CO(2) into the culture with the use of a counterflow sump system. Adding the CO(2) in the form of carbonated water resulted in utilization efficiencies of 81 +/- 11%. Archimedes screws proved superior to both paddle wheels and propellers as a means of circulating the water in the flumes. Insertion of foil arrays into the flumes to effect systematic mixing of the culture significantly enhanced production. The enhancement was greater when the foils were oriented at a small angle relative to the horizontal than when they were oriented at the same angle relative to the vertical. Light modulation effects are implicated as the probable cause of most of the enhancement. Substitution of electric power plant stack gases for pure CO(2) resulted in no significant change in the production of T. suecica grown in chemostat culture.

Optimization of microalgal production in a shallow outdoor flume.

The marine diatom Cyclotella cryptica was grown over a period of 13 months in a 48-m(2) shallow outdoor flume. The use of foil arrays at intervals of 1.2 m to effect systematic vertical mixing in the flume was found to significantly enhance microalgal production (p = 0.006). Average photosynthetic efficiencies (based on visible irradiance) with and without the foil arrays in place were 9.6 +/- 0.8 and 7.5 +/- 0.5% (+/-95% confidence intervals), respectively. A cost-benefit analysis indicated that the foil arrays were cost-effective if the value of the algae exceeded about $2.28 kg(1) of ash-free dry weight (AFDW). Parallel experiments performed in four 9.2-m(2) flumes showed that production was maximized when the cells were grown on a 2-day batch cycle between harvests rather than on a 1- or 3-day batch cycle. The optimum initial concentration (immediately after harvesting) of the algae was negatively correlated with the time interval between harvests and ranged from approximately 39 g AFDW/m(3) on a 3-day cycle to 213 g AFDW/m(3) on a 1-day cycle. The increase in production resulting from growth on a 2-day rather than a 1-day batch cycle was about 19% and was statistically significant at p = 0.0003. Growth of C. cryptica over a total period of 122 days during the 13-month study in the 48-m(2) flume under near-optimal conditions (2-day batch cycle, initial concentration 155 g AFDW/m(3)) resulted in an average production rate (+/-95% confidence interval) of 29.7 +/- 2.7 g AFDW/m(2) d.

Method for Assessing Heterogeneity in Turnover Rates within Microbial Communities.

A method is presented for determining both the average turnover rate and the standard deviation of the average turnover rate of the adenine nucleotide (AN) pool within a population of microorganisms. The method requires the calculation of the initial slope and curvature of a plot of AN specific activity versus time following the introduction of [H]adenine. An analysis of noise-corrupted data indicated that the method is capable of detecting a lack of uniformity in the turnover rate when the coefficient of variation of the turnover rate exceeds 39%. An analysis of field data revealed a significant lack of uniformity in the turnover rates of microbial communities in a marine sediment sample and freshwater pond but no significant nonuniformity in the turnover rates of microbial communities in a seawater sample and in a second freshwater pond. Although the method has been applied only to the analysis of AN turnover rates, it is applicable to any intracellular pool for which a suitable radioactive precursor exists.

High algal production rates achieved in a shallow outdoor flume.

A mass culture of Tetraselmis suecica grown in seawater enriched with only inorganic nutrients and CO(2) in a shallow outdoor flume containing foil arrays to effect systematic vertical mixing achieved average daily production rates of over 40 g ash-free dry wt (AFDW)/m(2) over periods as long as one month when grown on a three-day dilution cycle. Photosynthetic efficiencies associated with these high production rates averaged 8-11% based on visible irradiance. Operation of the system in a one-, two-, or four-day dilution cycle resulted in lower photosynthetic efficiencies of 6-7%. A remarkable feature of the three-day dilution cycle results was the fact that production on the third day after dilution averaged 60-70 g AFDW/m(2), and corresponding photosynthetic efficiencies averaged 13-19%. The high production rates and photosynthetic efficiencies achieved on the third day after dilution may have reflected the nonequilibrium nature of the production cycle and, in particular, the fact that the adaptation of the cells to changing light condition lagged behind light condition in the culture.

A simple algal production system designed to utilize the flashing light effect.

Arrays of foils similar in design to airplane wings have been placed in an algal culture flume to create systematic mixing. Vortices are produced in the culture due to the pressure differential created as water flows over and under the foils. In a flume having a flow rate of 30 cm/s, the foil arrays produced vortices with rotation rates of ca. 0.5-1.0 Hz. This rotation rate is satisfactory to take advantage of the flashing light effect if the culture is sufficiently dense. Solar energy conversion efficiencies in an experimental culture of P. tricornutum increased 2.2-2.4 fold with the foil arrays in place versus controls with no foil arrays and solar energy conversion efficiencies averaged 3.7% over a three-month period. Five-day running means of solar energy conversion efficiencies reached as high as 10% during the three-month period. The use of foil arrays appears to be an effective and inexpensive way to utilize the flashing light effect in a dense algal culture system.

Pharmacokinetics and tolerance of single intravenous doses of cefotetan disodium in male Caucasian volunteers.

Cefotetan, a third generation cephalosporin, in doses of 0.25, 0.5, 1.0 and 2.0 g was administered intravenously as the disodium salt to ten healthy male Caucasian volunteers and its pharmacokinetics and tolerance determined. The elimination half-life was 3.3 h. The drug was 88% plasma protein bound and 67% was recovered unchanged in the urine. HPLC and bioassay techniques for cefotetan plasma-concentration determinations gave virtually identical results. Cefotetan was well tolerated although half of the volunteers experienced transient mild to moderate diarrhoea. It is concluded that the pharmacokinetic disposition of cefotetan is similar in Caucasian and Japanese subjects and that the long elimination half-life, lack of detectable metabolism and high urinary excretion will result in plasma and urine concentrations in excess of the MIC of sensitive bacteria on a twice daily dosing regime.

The effect of clofibrate on glucose tolerance, insulin secretion, triglycerides and fibrinogen in patients with coronary heart disease.

The effects of clofibrate treatment have been monitored in a double-blind cross-over study conducted in 16 male patients with coronary heart disease. Most had latent diabetes mellitus with elevated and delayed insulin release after i.v. glucose administration. Blood glucose and insulin levels were measured during repeated i.v. glucose tolerance tests in each patient and serum triglyceride and plasma fibrinogen were estimated at intervals. Clofibrate treatment significantly lowered fasting blood glucose levels (p less than 0.01) and improved the glucose tolerance (p less than 0.01). Fasting plasma insulin levels and those at 30 min after glucose loading were reduced (p less than 0.05). Serum triglycerides (p less than 0.01) and plasma fibrinogen levels (p less than 0.05) were lowered during the treatment period. The change in k-value (glucose utilization) did not correlate to changes in triglyceride or fibrinogen. This study confirms the beneficial effect of clofibrate therapy on abnormal glucose tolerance observed by other workers. It is suggested that clofibrate acts by reducing peripheral insulin resistance.